1. Field of the Invention
This invention relates generally to the compensation of misalignment between substantially aligned supporting surfaces and more particularly concerns an apparatus which provides lateral compensation between a pair of misaligned shafts through angular deflection of a support member connected to one of the shafts.
2. Description of Prior Developments
Precision uniaxial movement devices, such as positioning tables, way slides, and carriages, used on manual, automatic, and numerical controlled machinery are known to require extreme accuracy of alignment during manufacture and assembly. In the case of positioning tables utilizing linear motion bearings and shafts, absolute parallelism and straightness of the shafts are required. Since this is in practice impossible to achieve, at other than a very high cost, the need has existed for a compensator which can accommodate lateral shaft misalignment, while maintaining the stiffness of the bearing system against compressive and tensile loading.
A source of shaft misalignment is known to originate from shaft nonlinearity wherein the straightness or cylindricity of the shaft is less than perfect. This misalignment results in a variation in the center to center distance between two aligned parallel shafts and can cause binding of linear bearings as they slide over the shaft surfaces. This variation and binding can occur even if the shafts are aligned as parallel as possible. In addition, a lack of parallelism between the two shafts, part tolerances and differential thermal expansion present further sources of shaft center to center distance variations.
The effects of such variations on non-compensated positioning systems include a lowering of the effective capacity of the bearings which slidably support the positioning table, greater wear and shorter life of moving and contacting components, greater friction resulting in greater drive force requirements and inconsistent performance of the positioning system.
Prior developments include two types of lateral compensators. The first type uses a linear motion bearing mounted in a cylinder of deformable material, such as rubber. While this provides a low cost lateral compensator, the device does not maintain the "vertical" stiffness of the bearing system. That is, the rubber cylinder readily deflects under compressive and tensile loading and often results in unacceptable distortion and displacement.
The second type of lateral compensator utilizes a precision linear slide to effect compensation. This however, represents a high cost solution to the problem.
While attempts have been made to eliminate center to center distance variations between a pair of substantially parallel shafts, such attempts have resulted in greatly increased system costs and have been less than completely satisfactory. Thus, a need exists for an economical compensator which will effectively compensate for lateral misalignment between a pair of substantially parallel supporting surfaces while actually reducing overall system costs while maintaining the stiffness of the bearing system against applied loads.